The present invention relates to an image forming apparatus equipped with a charger for electrically charging a photosensitive element and an exhaust fan for ventilating the image forming apparatus.
Generally, a known image forming apparatus electrically charges a photosensitive drum and emits laser light on this electrically charged photosensitive drum so that the electric potential of the exposed area (i.e., area on which the laser light is emitted) lowers to form an electrostatic latent image on the photosensitive drum. The image forming apparatus then supplies developer on this latent image to form a developer image, which is transferred on a paper so that a predetermined image is formed on the paper.
As one example of such an image forming apparatus, Japanese Laid-open Patent Application No. 2005-292356, which corresponds to US 2005/0220479A1, discloses an image forming apparatus equipped with a scanner unit for scanning laser light and a process unit positioned below the scanner unit with a predetermined gap interposed therebetween. This image forming apparatus mainly includes in the process unit a photosensitive drum for carrying developer images, a charger for electrically charging the photosensitive drum, and an exposure window through which laser light from the scanner unit is emitted on to the photosensitive drum. The charger and the exposure window are arranged adjacent to each other.
This kind of image forming apparatus is usually provided with an exhaust fan for mainly discharging heat from the inside of the apparatus. Air between the scanner unit and the process unit is drawn by the exhaust fan from the exposure window toward the charger so as to perform a heat discharging operation, etc.
However, when the exhaust fan draws air between the scanner unit and the process unit, there may be a possibility that air flows into the process unit through the exposure window, etc. and then flows out from the process unit through the charger. If this happens, contrary to ion flow generated during the electric charge by the charger (i.e., airflow generated by the movement of ions upon electric charge) and directed from the charger to the photosensitive drum, the operation of the exhaust fan generates airflow which flows in the counter direction of the ion flow. As a result, efficiency of electric charge may be decreased by this counter flow.
In view of the foregoing drawback of the conventional image forming apparatus, the present invention seeks to provide an image forming apparatus which can prevent a decrease in efficiency of electric charge.